An optical time-domain reflectometer (“OTDR”) is an opto-electronic instrument used to characterize an optical fiber. A typical OTDR injects a series of optical pulses into the fiber during a testing process. From the same end of the fiber, the OTDR also extracts light that is scattered and reflected back from points in the fiber where the index of refraction changes. This process is equivalent to the manner in which an electronic time-domain reflectometer may measure reflections caused by changes in the impedance of the cable under test. Accordingly, the strength of the return pulses is measured and integrated as a function of time, and is plotted as a function of fiber length.
OTDRs have conventionally been standard equipment for the characterization of optical fiber. Specifically, it is well known that OTDRs may characterize the loss and length of an examined fiber during manufacture, during warehousing, during installation, and during splicing. OTDRs are also used in measuring optical return loss in the fiber, as well as locating faults in the fiber, such as breaks. Faults or failures in the fiber may be costly, in terms of repairing the fiber, as well as have adverse effects on service (e.g., disruption or loss of service). Any improvements in OTDRs have conventionally required the use of more sensitivity and more expensive devices and components. Specifically, improvements in sensitivity are typically achieved through launching more light into a test fiber and using OTDR detectors having less noise. While conventional OTDR devices may make adjustments in sensitivity to increase the range of the device, these adjustments do not improve the resolution limitations caused by polarization effects in the fiber.